1. Concept of Maintenance

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AIRCRAFT MAINTENANCE

(437309)

BY

SAMRIT RATANACHENA

Mobile 084 3224277 (24/7)

E-mail address [email protected]

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SECTION 1

Concept of AircraftMaintenance

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WHAT IS AN AIRCRAFT

MAINTENANCE? Aircraft maintenance is the overhaul, repair, inspection or

modification of an aircraft or aircraft component.

Maintenance may include such tasks as ensuring compliance with

Airworthines Directives or Mandatory/ Alert Service Bulenttins. Aircraft maintenance is highly regulated. There are various airworthiness

authorities around the world. The major airworthiness authoritiesinclude:

At the completion of any maintenance task a person authorized by the

national airworthiness authority signs a release stating thatmaintenance has been performed in accordance with the applicableairworthiness requirements.

(FAA USA)

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REASONS FOR MAINTENANCEJ an-13

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Reasons for Maintenance

To keep performance, reliability and availabilitywithin design limits at minimum cost.

Deterioration with age examples are fatigue,wear and corrosion.

Chance failure examples are tyre burst, excessstructural loads.

Processes that affect an aircraft


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AIRCRAFT MAINTENANCE CHECKS

Aircraft maintenance checks are periodic inspections that have to bedone on all commercial/civil aircraft after a certain amount of time orusage Airlines and other commercial operators of large or turbine-powered aircraft follow a continuous inspection program approved byThai DCA or Local Authority.

Airlines and airworthiness authorities casually refer to the detailed

inspections as "checks", commonly one of the following: A check, Bcheck, C check, or D check.

A and B checks are lighter checks, while C and D are considered heavierchecks.

Commercial/Air Charter/Civil aircraft and airworthiness authoritiescasually refer to the detailed inspections as "checks", commonly one of

the following: 50/100/150/200 Hour Inspection, Operation 1/2/3/ 4,Inspection,Phase 1/2/3/4 Inspection and etc .

The military aircraft normally follow specific maintenance programmeswhich may be or not similar to the commercial/civil operators.

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Maintenance consist of 4 type;

Corrective Maintenance: CM (Breakdown Maintenance Run to Failure) -

Preventive Maintenance: PM (Planned maintenanceCalendar-based maintenance Historicalmaintenance)

Predictive Maintenance (Condition-based maintenance:CBM) -

Proactive Maintenance (Design out Maintenance Precision Maintenance) -

Form of Maintenance - General


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1. CORRECTIVE MAINTENANCE : CM

Corrective Maintenance: CM

(Breakdown Maintenance Run to Failure)


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2. PREVENTIVE MAINTENANCE : PM

Preventive Maintenance: PM

(Planned maintenance Calendar-based maintenance Historical maintenance)

(interval)


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3. PREDICTIVE MAINTENANCE : CBM

Predictive Maintenance(Condition-based maintenance: CBM)

, ,


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4. PROACTIVE MAINTENANCE : DM

Proactive Maintenance (Design out Maintenance Precision Maintenance)

, Operators


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REACTIVE MAINTENANCEJ an-13

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PROACTIVE MAINTENANCEJ an-13

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TYPES OF SCHEDULED MAINTENANCE

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Light or Line Maintenance: Preflight Check Daily Check Weekly Checks A (Multiple A) and B Checks

Base or Heavy Maintenance: C (Multiple C) and D Checks

Shop or Component Maintenance: Maintenance on components when removed from aircraft


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TYPES OF AIRCRAFT MAINTENANCE

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Routine maintenancecheck Replacement of life

limited items Cleaning Performance of

modification originatedwork Rectification of

deferred defects

Activities originated from: Cabin log bookTechnical log book Ground findings

Maintenance

PlannableUnplannable

Scheduled Unscheduled


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TYPE OF MAINTENANCE

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Unscheduled (or corrective):

Maintenance performed to restore

an item to a satisfactory condition

by providing correction of a known

or suspected malfunction and/or

defect.

Unscheduled maintenance action is

performed if there is a pilot report

or a complaint from the scheduled

maintenance.

Scheduled:

Maintenance performed at defined

intervals to retain an item in a

serviceable condition (availability, safety

and reliability to their inherent levels)

Scheduled maintenance action is

performed according to the Maintenance

Program requirements

Servicing:

Any act of replenishment for the

purpose of maintaining the inherent

design operating capabilities of an

item.


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RELATIONS IN AVIATION MAINTENANCE

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Manufacturer

Operator

Maintenance

AircraftMaintenance


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NEEDS OF AVIATION MAINTENANCE

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1. Safety

2. Availability

3. Economic

Continued of Airworthiness, Regulation, Cost ofAccident, Company Reputation, etc

Cost of delay, Cost of cancel, CompanyReputation, etc

Profit, Stock, Bonus, etc


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ELEMENTS OFDOWN TIME AND REPAIR TIME

Realization Time: Time elapses before the fault condition becomesapparent.

Access Time: Time from realization that a fault exists, to makecontact with displays and test points and so commence fault finding.This does not include travel but the removal of covers and shields

and the connection of test equipment. Diagnosis Time: Time for fault finding.

Spare part procurement: Time taken to move parts from a depot orstore to the system. Part procurement can be from the tool box, bycannibalization or by taking a redundant. The

Replacement Time: This involves removal of the faulty LRA (LeastReplaceable Assembly) followed by connection and wiring, asappropriate, of a replacement.

Checkout Time: This involves verifying that the fault condition nolonger exists and that the system is operational.

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ELEMENTS OFDOWN TIME AND REPAIR TIME

Alignment Time: As a result of inserting a new module into thesystem adjustments may be required.

Logistic Time: Time consumed waiting for spares, test gear,additional tools and manpower to be transported to the system.

Administrative Time: This is a function of the system usersorganization. Typical activities involve failure reporting allocation ofrepair tasks, manpower changeover due to demarcationarrangements, official breaks, disputes, etc

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MECHANISMS OF FAILURE

Some of failure mechanisms in aircraft and systemsequipments :

Material failure

Parameter drift

Leakage

Contamination

Software failure

Electromagnetic Interference Fraud

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CAUSE OF FAILURE

Common areas linked to causes of failures:

Design Manufacturing

Maintenance

Purchasing Operator

Quality system

Data

Sabotage or enemy action

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SOURCES OF FAILURE

Categories illustrate some less obvious potential basic sources of failure:

Ignorance -a designer, manufacturer, maintainer or operator isunaware of the risk in the decision he is making or the activity he isundertaking.

Lack of data -a sub-category of ignorance but one over which themaintenance system has some control.

Negligence -While the individual or organisation is aware of thecorrect action, this is not carried through. Errors can be madethrough inattention. The extreme case is wilful negligence whichmay be chargeable as criminal negligence.

Poor planning -lack of adequate planning can trigger a chain ofcircumstances leading to a system failure

Sabotage or enemy action -where deliberate hostile action isinvolved.

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BREAKDOWN MAINTENANCE TASKS

Fail-repair: Failed item is restored to its operational state.

Salvage: Concerned with disposal of nonrepairable material and use ofsalvaged material from nonrepairable equipment/item in the repair,overhaul, or rebuild programs.

Rebuild: Concerned with restoring an item to a standard as close aspossible to original state in performance, life expectancy, andappearance.

Overhaul: Restoring an item to its total serviceable state as permaintenance serviceability standards, using the inspect and repair onlyas appropriate approach.

Servicing: Servicing may be needed because of the correctivemaintenance action, for example, engine repair can lead to crankcaserefill, welding on, etc.

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DIRECT OPERATING COST BREAKDOWN

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Fuel

(25%)

Crew (11%)Landing /

Navigation

taxes (9%)

Insurance(2%)

Depreciation /Finance

(41%)

Scheduled

(3.5%)

Unscheduled

(8.5%)

Maintenance (12%)

LabourMaterial

50 50

SystemsPowerplant Structure

50 40 10

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AIRLINES OPERATING COST

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LCC (Life Cycle Cost) : Total operating cost over the life of theaircraft or engine

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LCC (Life Cycle Cost) : Total operating cost over the life of the aircraft orengine

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Cost

Times-3 yrs 0 2 to 3yrs

15 305

Reimbursement CostWarranty

Maturity

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TOC (Total Operating Cost) which sometimes called cost ofownership) [TOC = DOC + IOC]

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IOC (Indirect Operating Cost) : Other costs beyond DOC such asMarketing, Passenger services, Aircraft handling andAdministration

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DOC = DMC + IMC + Fuel + Landing and navigation fees +Flight crew expenses + Insurance depreciation + Financing ofaircraft and spares

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DMC (Direct Maintenance Cost) : Productive labour and material consumed tomaintain the aircraft

IMC (Indirect Maintenance Cost) : Other costs attributed to maintenance such asadministration, engineering, training, supervision, amortisation of tools and facilities

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MAINTENANCE COST : DMC VS IMC

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A330/A340 DIRECT MAINTENANCE COST (DMC)SPLIT IN COMPONENT

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BOEING TYPICAL INSPECTIONJ an-13


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BOEING TYPICAL INSPECTIONINTERVAL

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170737-100

737-200125 750 3,000 20,000 700 2,840 21,000

737-300

737-400

737-500200 3,200 20,000 220 3,300 21,500

MD-80 450 3,500 15,000

72780 400 16,000 18,5005,000

757500 FH (Sys.)

300 FC (Stru.)

6,000 FH

(Sys.)

3,000 FC

(Struc.)

A

World weighted fleet interval (FH)Recommended initial interval (FH)

AB BC CD

(StructuralInspection)

D(StructuralInspection)

Aircraft

Letter

check

747-400Cathay Pacific 650 6,750 30,000

500 or70 days

777

(Cathay Pacific)

150

days365 Daysor 3000 hrs

?

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AIRBUS TYPICAL INSPECTION INTERVALJ

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A

Recommended interval

CD=4C

Aircraft

Lettercheck

A380Objective:

750 FH

Objective:

24 months

Structural inspection

A310

A300-600

400 FH

Initial: 250 FH

15 Months

Initial: 12 months

FD threshold: 18,000 FC

ED threshold: 10/7.5/5/2.5 years

A330

A340

700 FH

500 FH

18 months

15 months

FD threshold: 20,000/8,000 FCED threshold: 10/5/2.5 years

5 YearsCathayPacific

15 MonthsA319

A320

A321

500 FHFD threshold: 24,000 FCED threshold: 9/5/2.5 years

5 Years

CathayPacific

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LAWS & REGULATIONS

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NEW CONCEPT IN AVIATIONS

Aviation is changing day by day.How it is affecting us ?

Change In Regulation FAR/EASA 21/61/66/145/147

Type Rating Training Maintenance Control Manual

Maintenance Procedure Manual Quality Assurance Manual

Safety Management System English for Aviation Language Human Factors Type certificates

Certificate of Airworthiness Noise Certificate

Export Airworthiness Certificate

Airworthiness Management Maintenance

Continuing Airworthiness Management Airframe and Engine Licences & Electrical, Instrument and Radio

System Licences

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FURTHER READING

Aviation Maintenance Management by Kinnison, H.A. ;McGraw-Hill; 2004

Engineering Maintenance: A modern approach by DhillonB.S.; CRC press; 2002

Documents

1. Concept of Maintenance